Regarding work vehicles such as a tractor and a wheel loader, an opening/closing fulcrum shaft is arranged in the rear portion of a hood for covering an engine, and the hood is rotated about the opening/closing fulcrum shaft, for the purpose of improving the efficiency of maintenance work for the engine arranged in the front of a travelling vehicle body. Also, a technology of purification treatment has been known theretofore, wherein a case (hereinafter referred to as “DPF case”) in which a diesel particulate filter is internally provided, and a case (hereinafter referred to as “SCR case”) in which a urea selective reduction catalyst is internally provided are provided in the exhaust path of a diesel engine as an exhaust gas purification device (exhaust gas after-treatment device), and the exhaust gas is introduced into the DPF case and the SCR case, thereby purifying the exhaust gas discharged from the diesel engine (for example, see Patent Literatures 1 to 4).